1. Field of the Invention
The present invention relates to a battery pack which is detachably attached to electric equipment such as an electric tool and supplies electric power to the electric equipment.
2. Description of the Related Art
Electric equipment such as an electric tool includes a battery pack which includes a rechargeable battery and is detachably attached to the main unit of the electric equipment. Such electric equipment is useful as a cordless-type tool in construction sites and the like. Since the battery pack can be detached from the main unit of the electric equipment, the detached battery pack can be attached to a charger so that the battery pack is charged. Thus, the battery pack can be repeatedly used. A charger for charging this type of battery pack has been in practical use and includes an attachment portion that is arranged on the upper surface of the charger case and detachably holds the battery pack. Charging terminals are exposed from the attachment portion. In this charger, external connection terminals of the battery pack are connected to the charging terminals when the battery pack is attached to the attachment portion so that charging power is supplied through the charging terminals to charge the battery pack (see Laid-Open Patent Publication No. JP 2007-280679 A).
Also, the battery pack has a lock structure that holds the battery pack on the attachment portion of the charger for preventing the battery pack from being detached from the attachment portion. For example, as shown in FIG. 30, the lock structure can include a hook-shaped lock hook 97 that protrudes from the battery pack 90 and can engage with a lock opening 93 arranged in the attachment portion 92 thereby preventing detachment of the battery pack 90. Accordingly, the battery pack 90 includes a spring that biases the lock hook 97 in the protruding direction. When users press the lock hook 97 with their finger, the lock hook 97 can be disengaged from the lock opening. The battery pack 90 has a structure that allows the lock hook 97 to protrude/retract from/into the battery pack.
See also Laid-Open Patent Publication Nos. JP 2009-212583 A and JP 2009-60165 A.
On the other hand, if water comes into the battery pack, the terminals of the rechargeable battery or the electronic circuit may be short-circuited. For this reason, the battery pack preferably has a waterproof structure. However, since the battery pack has the movable part in the lock structure, it is not easy to provide a completely waterproof structure in the battery pack. In particular, since the lock hook is required to move, the opening is necessarily formed so as to allow the lock hook to protrude. For this reason, there is a problem that water may come into the casing of the battery pack through this opening. In addition, if water enters the battery pack, it is not easy to drain the water from the battery pack. The water may move to the rechargeable battery or the electronic circuit board, and may cause unintended electric conduction.
Also, the battery pack has an opening that is arranged in a part where the output terminals are arranged for connection to the electric equipment or the like. Thus, the output terminals are exposed through the opening externally of the battery pack. There is also a problem that water may come into the case through this opening.
The present invention is devised to solve the above problems. It is a main object to provide a reliable battery pack having an improved waterproof structure.